Bar filters are applied in apparatuses, in which a liquid, in which magnetic particles have been suspended is filtered for removing the magnetic particles from the liquid.
Such an apparatus is used for removing phosphates from waste water. Therefore, phosphates are chemically bonded to magnetic material, for instance magnetite, after which the liquid thus obtained is fed through a magnetic filter. Therein the phosphate-magnetite particles adhere to the bars of the magnetic filter, in which the filter is increasingly filled with these particles, which have to be removed from the liquid. At a certain moment the filter is filled to such extent, that the passage thereof is limited considerably. Then the filter has to be cleaned.
Whereas such cleaning actions interrupt the real action of the filter, it is necessary to limit the frequency thereof as far as possible. This frequency can be limited by flushing only when a filling to the highest extent, i.e. as homogeneous as possible, is obtained.
The aim of the present invention is to provide such a filter, in which the filling of the filter is as much homogeneous as possible.
This aim is reached, in that the distance between the bars in the direction of the field lines is such, that the gradient of the magnetic field is constant.
As a consequence of this dimensioning, leading to a constant gradient of the magnetic field, the magnetic particles and the liquid, which are filtered from the flowing liquid by means of the magnetic filter, a force which is as constant as possible, so that the chance, that they are drawn to one of both adjacent bars as an equal magnitude at all locations within the filter. This leads to an even filling of the filter.
According to a preferred embodiment the density of the bars in a plane perpendicular to the bars is constant. Also this feature leads to an improvement of the evenness of the filling of the filter, as the space between the bars is mutually constant, so that the space to be filled by the magnetic particles is equal.
Subsequently the present invention will be elucidated with the help of the accompanying drawings.